1. Field of the Invention
The present invention relates to a radiation image detector, in particular, to a moisture prevention structure of the detector.
2. Description of the Related Art
A variety of direct type radiation image detectors is proposed and put into practical use in the medical and other industrial fields. These detectors are constructed to receive radiation transmitted through a subject to generate charges, and to record a radiation image of the subject by storing the charges therein.
U.S. Pat. No. 6,770,901 proposes an X-ray imaging device that uses amorphous selenium as a photoconductive layer, and X-rays are irradiated on the photoconductive layer with a bias voltage being applied thereto, thereby charges generated therein are detected. Such detectors are preferable to be fully covered by a moisture-proof structure, since sensitivity of the detectors is gradually degraded due to environmental moisture, in addition to increased image defects.
One such moisture-proof structure is proposed as described, for example, in Japanese Unexamined Patent Publication No. 2005-286183, in which a frame-like spacer is provided on the detector, and hardening synthetic resin is filled between the frame and an accessory plate disposed thereon, thereby a moisture-proof structure is formed.
Forming the frame-like spacer, however, is difficult depending on the material used, and simpler moisture-proof structures have been demanded.
Further in a radiation image detector used for mammography, for example, it is preferable that the amorphous selenium layer or the like be extended (provided), as close as possible, to the edges of the detector, so that mammography is performed to a portion as close to the chest wall as possible. But, it has been difficult to satisfy both the requirement related to the arrangement of the amorphous selenium layer or the like and moisture proof capabilities.